I doubt that you will find a (functioning) transformer for the SA-20; I also don't have a more info about the transformer. If you really want to make a new transformer, the above schematics should be enough - the power stage winding should be 2*48V under load with about 10 amps, the rest is already defined by the schematics.
All the best!
All the best!
This discussion raises several red flags. MOSFETs are actually very tricky to test, even if removed from circuit (they retain charge across the gate-source junction, so can fool DC based testers). Power transformers have low enough winding resistances as to be tricky to measure with ordinary DVMs with ordinary leads. It's very difficult to judge the experience level of strangers on a discussion forum, so please forgive me if I, a stranger, question the validity of measurements and assumptions.
All good fortune,
Chris
All good fortune,
Chris
Hi Chris,
absolutely correct; you may check the transformer with a variac on the primary side without any secondary load - if there is no exceptional current flowing and after some time the transformer is not getting too warm, the transformer may be ok
absolutely correct; you may check the transformer with a variac on the primary side without any secondary load - if there is no exceptional current flowing and after some time the transformer is not getting too warm, the transformer may be ok
I learned a new trick over at another forum: If you have a Variac, turn it down to 12VAC, then measure the windings and multiply by ten. You'll be less likely to cause an injury that way. No Variac? Find an old Lionel train transformer and run it up to 12VAC, with it connected to the primary. I.e., set the voltage with the primary as a load.
FWIW, even the primary will make the continuity test beep, depending upon its threshold. Almost every secondary 12V or less will read less than 1 Ohm.
FWIW, even the primary will make the continuity test beep, depending upon its threshold. Almost every secondary 12V or less will read less than 1 Ohm.